Copper-lead alloys



United States Patent No Drawing. Application September 24, 1951, Serial N o.'248,092

Claims priority, application Germany October 4, 1950 7 Claims. (Cl. 75-463) The present invention relates to improved copperlead alloys, and more particularly to copper-lead alloys containing at least one alkaline earth metal, preferably calcium.

The copper-lead alloys containing from 10% to 50% of lead, known under the name of lead bronzes, are excellent bearing alloys; but possess the disadvantage that they are difficult to hot form, because of the occurrence of liquid lead on heating, and practically cannot be cold formed. Their excellent break in and emergency run (on break-down of the oil film) properties are also diminished when additions of alloying components, such as tin, aluminum, manganese, nickel, iron or cadmium, are incorporated therein for hardening such alloys or to obtain a fine lead distribution in the alloys. Even on increase of the Brinnell hardness of such alloys to over about 40 by such additions, a lowering of the break-in and emergency run properties of the lead bronze bearing alloys becomes noticeable. As previously no other bearing alloys were known which had a higher strength and hardness than binary lead bronzes and at the same time the emergency run characteristics of such lead bronzes, it was necessary to be able to utilize the excellent emergency run characteristics of the relatively soft alloys to employ them in combination with stronger carrier metals. Aside from the ever present danger that the bearing metal may separate from the backing metal, the difiiculties in the production of such composite bearings increase their costs considerably.

It is the object of the invention to provide lead bronze bearing alloys which avoid the aforementioned ditficulties.

In accordance with the invention, it has been discovered that lead bronzes of increased hardness which have the same emergency run and the same resistance to wear of the binary lead bronzes can be produced by additions of at least one alkaline earth metal, particularly calcium. The objects of the invention are achieved by alloys of the following composition:

1.0% to 9.5% lead 0.3% to 8% alkaline earth metal Remainder copper.

Alloys in which the alkaline earth metal is calcium with ratios of calcium to lead larger than 1:25 and smaller than 1:1 are preferred.

Alloys containing 2.5% to 5% of lead, 1.4% to 3% of calcium and the remainder copper are exceptional in that they have many fields of application.

The alloys in accordance with invention are easily prepared by melting the components with or without the use of pre-alloys, and are cast without difiiculty.

The hardness of the alloys increases with increase in calcium content. With constant calcium content, the hardness increases as the lead content is lowered. In cast condition, the alloys in accordance with the in- 2,750,287 l atented June 12, 1956 ICC vention, depending on the calcium content, can have a Brinnell hardness of from about 45 to over 100.

The alloys in accordance with the invention may be hot formed by pressing, rolling and forging into tubes, profiles, bands and presseds'hapes; and can also be cold formed by drawing or rolling. 1

The Brinnell hardness of the alloys in accordanc with the invention can be increased to over by these cold or hot working operations.

Additional hardening of the alloys according to the invention can be achieved by the addition of alloying components normally employed in the hardening of copper alloys such as iron, nickel, manganese, aluminum, tin and cadmium; either singly or in combination; in quantities not exceeding 3% of the alloy. However, it is usually preferable to achieve the desired hardness by the addition of a sufficient quantity of calcium or other alkaline earth metal.

The hot workability of the alloys according to the invention is achieved in that the low melting lead is to a greater or lesser extent bound as relatively a higher melting intermolecular compound with the alkaline earth metal. It is therefore possible to anneal the alloys at temperatures over 800 C. without causing deleterious sweating-out of the lead, as is often the case with the normal lead bronzes. The relatively higher warm strength of the present alloys is also caused by the presence of the intermolecular compounds.

Further advantages of the alloys according to the invention are their high resistance to wear and their good turning and cutting properties, even on automatic machines. It is also important that even relatively soft steel shafts are not seized by the alloys according to the invention.

The pure lead phase in the alloys which diminishes the hot workability thereof is more centainly avoided in the alloys according to the invention, the larger the ratio of calcium to lead and especially When the ratio exceeds 1:2.5, which corresponds to the intermetallic compound CazPb.

Also the other unexpected improvements which are obtained by the addition of calcium or other alkaline earth metals are caused by the intermolecular compound formation, as the improvement increases with an increase in intermolecular compound content.

While the invention has primarily been described with reference to calcium; the other alkaline earth metals, such as strontium and barium have similar eifectsbut to a lesser extent, and consequently calcium can be replaced in part or entirely by other alkaline earth metals.

The excellent workability, the large range of hardness attainable in combination with the good emergency run properties of the alloys and the other advantageous properties thereof, give the alloys a very general utility which goes beyond their use as bearing materials. They can be employed in the form of pressed and rolled products; such as rods, tubes, profiles and bands; in the production of machine parts which are subjected to wear by sliding or rubbing action; especially shells, bushings, valves and driving elements; or such parts can be formed directly from the alloys in accordance with the invention by pressing. If desired the alloys according to the invention can be employed in the production of plated or clad articles; for example, by co-rolling an alloy according to the invention with steel or another metal and then employing the clad product to produce the desired article.

I claim:

1. An alloy consisting of 1.0% to 9.5% of lead, 0.3% to 8% of at least one alkaline earth metal and the remainder copper.

2. An alloy consisting of 1.0% to 9.5% of lead, 0.3% to 8% of calcium and the remainder copper.

3. An alloy in accordance with claim 1, having added thereto at least one metal having a hardening eifect on copper alloys selected from the group consisting of nickel, iron, manganese, aluminum, tin and cadmium, the total addition being not more than 3% 4. An alloy consisting of 1.0% to 9.5% of lead, 0.3% to 8% of calcium and the remainder copper, the ratio of calcium to lead being greater than 122.5 and less than 111.

5. An alloy consisting of 2.5% to 5% of lead, 1.4% to 3% of calcium and the remainder copper,

6. An article of manufacture having a surface subject to wear composed of an alloy consisting of 1.0% to 9.5% of lead, 0.3% to 8% of at least one alkaline earth metal and the remainder copper.

7. A bearing whose wear surfaces are composed of an alloy consisting of 1.0% to 9.5% of lead, 0.3% to 8% of at least one alkaline earth metal and the remainder copper.

References Cited in the file of this patent UNITED STATES PATENTS 1,988,153 Boltons Jan. 15, 1935 2,018,417 Peyinghaus Oct. 22, 1935 2,068,322 Hardy Jan. 19, 1937 2,157,121 Darby et a1 May 9, 1939 2,379,435 Hensel July 3, 1945 2,381,497 Hensel et a1 Aug. 7, 1945 2,460,991 Le Brasse et a1 Feb. 8, 1949 2,466,700 Grodsky Apr. 12, 1949 

1. AN ALLOY CONSISTING OF 1.0% TO 9.5% OF LEAD, 0.3% TO 8% OF AT LEAST ONE ALKALINE EARTH METAL AND THE REMAINDER COPPER. 